1. Field of the Invention
The present invention relates to a slide fastener used for joining cover sheets for seats of cars, or joining carpets, or tapestries and constructed to let a slider slip off in use.
2. Description of the Prior Art
The first type of slide fastener is used mainly for joining cover sheets for seats of cars. In this type of slide fastener, after a slider moves all the way to the terminal end of the slide fastener for joining the cover sheets, the slider is left to remain on the terminal end.
The second type of slide fastener used for joining carpets, artificial turf-mats for ball parks is described in Japanese Utility Model Publication No. 50-31122 and Japanese Utility Model Publication No. 51-4804. This type of slide fastener has no end stop on one end or the upper end. In use, a slider moves the length the slide fastener and passes beyond the upper end so that it slips off the slide fastener. The absence of an upper end stop is made up for by a separate bifurcated wire clip or a bifurcated flat plate clip, which clasp the terminal end of the slide fastener in order to keep the cover sheets from accidental separation.
Japanese Utility Model Publication No. 3-3272 discloses the third type of slide fasteners used on an annular head rest of a seat of an automobile. The slide fastener has one end provided with a pin-and-box type separate device and the other end provided with no end stop so as to permit a slider to pass beyond said other end and slip off the slide fastener. After the slider slips off the slide fastener, a separate annular clam is fitted over the slide fastener to prevent the slide fastener from separating from each other.
However, these conventional slide fasteners suffer from disadvantages.
In case that the first type of slide fastener is used on a cover sheet for a car seat, the slider left on the terminal end of the slide fastener is prone to impart to a driver or a passenger an offensive feeling. That is why this type of slide fastener is limited very much in the application. Furthermore, the slider is likely to accidentally slip away from the terminal end of the slide fastener under severe stresses, thus opening the slide fastener unexpectedly.
The second type of fastener is quite free from the offensive feeling which would be caused by a slider's remaining at the terminal end of the slide fastener. However, after the slider slips off the slide fastener, the separate wire or plate clip must be clipped to the terminal end of the slide fasteners so as to prevent accidental opening of the slide fastener. Moreover, the clip must have mechanical strength enough to put up with severe stresses which are likely to be exerted on the sheets. If it is deficient in strength, the clip will break or get detached from the slide fastener under severe stresses.
The third type of slide fastener has the annular clamp fitted thereover at its terminal end. Since being bulky, the annular clamp makes the overlying cover sheet swollen locally and causes an unpleasant feeling on a passenger.